large numbers

But what is the most common vertebrate species on the planet? And how many of them are there?

The answer, it turns out, is the humble bristlemouth fish (Latin family name Gonostomatidae), and it numbers in the Hundreds. Of. Trillions. (And possibly, according to some estimates, in the quadrillions.)4 An unassuming family of fishes, the bristlemouths range in size from 1 to 11 inches5 and prefer the mid-ocean depths of about 0.5 to 1 mile down.6